High specific speed radial flow fan



wxllt 74 June 15, 1965 Filed May 31, 1963 Fig] YASUTOSH] SENQO HIGH SPECIFIC SPEED RADIAL FLOW FAN 4 Sheets-Sheet 1 INVENTOR.

YASUTOSH/ SENOO ATTORNEY June 1965 YASUTOSHI SENOO 3,189,259

HIGH SPECIFIC SPEED RADIAL FLOW FAN Filed May 31, 1963 4 Sheets-Sheet 2 INVENTOR.

YA S U TOSH/ SE N00 A TTORNE) June 15, 1965 YASUTOSHI SENOO 3,189,259

HIGH SPECIFIC SPEED RADIAL FLOW FAN Filed May 31, 1963 4 Sheets-Sheet s Fig.3

INVENTOR.

YA S U TOSH/ 85 N00 @ZZKMM A TTORNE Y June 15, 1965 YASUTOSHI SENOO HIGH SPECIFIC SPEED RADIAL FLOW FAN 4 Sheets-Sheet 4 Filed May 31, 1963 mum INVENTOR. msurosm samba.

A TTOR/VEY United States Patent rett Qorporation, Los Angeles, Qalih, a corporation 0% California Filed May 31, 1963, Ser. No. 234,437 3 Claims. (Cl. Z3lll19) This invention relates generally to fluid-moving mechanism. More particularly, the invention is directed to air fans or blowers of the centrifugal or radial flow type which are not provided with a scroll. Still more particularly, the invention is directed to a radial flow air fan adapted especially for use on ground eiiect machines or in other installations wherein large volumes of air at low pressure are required in contrast to relatively high pressure. In such installations provided heretofore, the fans employed have been large, cumbersome devices operating at relatively low speeds.

It is an object of this invention to provide a high specific speed radial flow fan of relatively small size which will be ideally suited for use in ground efiect machines.

Another object of the invention is to provide aradial flow fan so constructed that the velocity of the air entering the inlet will exceed the outlet velocity by a predetermined ratio whereby flow separation of the air as it passes through the fan and ineiliciencies caused thereby will be prevented.

Another object or" the invention is to provide a radial flow fan having a large outlet-to-inlet ratio, so that the velocity of the air decreases as it moves from the inlet to the outlet through the impeller and consequently no separation of boundary layer flow will take place.

Still another object of the invention is to provide a radial flow fan having an axial inlet and a radial outlet from which the air is discharged radially in all directions substantially at right angles to the axis of the fan, the fan impeller blades being confined primarily to a relatively short radius bend which connects the inlet and outlet whereby the over-all height and diameter of the complete fan will be restricted when compared to a conventional radial flow fan, the passage between the inlet and the outlet having a smaller diameter at the inlet than a conventional radial flow fan, the height of the outlet, considered when the axis of the fanis vertical, being greater than that of a conventional radial flow fan. Consequently some reduction of meridional velocity of the air will take place as it flows through the impeller between the inlet and the outlet. This reduction of velocity or diffusion within the fan makes it more adaptable for use in ground effect machines because the size of the clili'user usually provided between the fan and the nozzle of the machine may be reduced or the necessity for a diffuser at such location eliminated. By causing the air to flow radially in all directions in a plane normal to the axis of the fan, the unit is more adaptable for use in ground eliect machines than conventional radial fan units in which the air delivered bythe fan is collected in a scroll and discharged through a duct extending tangentially therefrom.

Since a fan formed in accordance with the present invention requires no diffuser vanes at the exit of the impellet, the maximum diameter of the unit is determined by the impeller diameter. A substantial savings in size and weight of the unit compared to a conventional fan with an exit vane diffuser is thus secured.

An object of the invention also is to provide a fan mechanism having housing means which forms a passage with an inlet of annular cross section and an outlet extending radially in all directions at right angles to the axis of theinlet, guide vanes being radially directed across the inlet and inclined to impart an initial whirling motion to the fluid, the housing receiving an impeller with blades confined substantially to the turn between the axially and radially extending portions of the passage, the blades on the impeller being inclined and the impeller driven in the direction opposite to the initial whirl so that fluid will issue from the outlet in substantially radial directions, the effective cross-sectional area of the outlet being greater than that of the inlet whereby a diffusion of fluid and decrease in the velocity thereof will take place as it flows from the inlet to the outlet through the impeller with a consequent increase in pressure.

Other objects and advantages of the invention will be apparent from the following description of one form of the invention which has been illustrated in detail in the accompanying drawings.

In the drawings:

FIG. 1 is a longitudinal axial sectional View taken through a fan formed in accordance with the present invention;

FIG. 2 is a horizontal transverse sectional View taken on the plane indicated by the line II-II of FIG. 1 showing the rotor of the fan in front elevation;

FIG. 3 is a similar view on a plane indicated by the line IIIIII of FIG. 1 showing inlet guide vanes in elevartion;

FIG. 4 is a side elevational view on an enlarged scale of the fan rotor showing an end elevation of one of the blades; and

FIG. 5 is a developed view of a section taken on the arcuate line V-V of FIG. 3 showing the relation of the inlet guide vanes to the fan rotor blades.

A more particular reference to the drawings will show that the fan selected for illustration includes a casing ill having an inlet 11 and an outlet 12. The inlet extends in an axial direction while the outlet extends radially in all directions in a plane at right angles to the axis of the inlet. In the illustration, the casing appears to be formed of one piece. It is obvious that the construction may be made of as many pieces as desired to secure the best method of fabrication.

The casing 10 has a smooth tubular inlet wall 13 which is connected with a first wall 14 extending at right angles to the axis of the portion 13. A second wall 15 also extends at right angles to the tubular portion 13 and is spaced from the wall 14 to provide the annular outlet. The wall 15 has a central opening 16 disposed axially with respect to the inlet and this opening receives a shaft 17 to support, for rotation in the casing, a fan impeller designated generally by the numeral 18. The wall 15 is pro vided with suitable bearing (not shown) to rotatably support the shaft.

The tubular section 13 or the casing receives a plurality of stator vanes 26) which are connected with the wall 13 and project radially inwardly into the inlet. The stator vanes 20 may be adjusted to vary the inclination or tilt thereof which imparts a preswirl to the air as it enters the fan. At the inner ends these stator vanes receive and support a conoidal spinner element 21 which serves to guide the air as it enters the inlet and cooperates with the wall 13 to convert the inlet from a circular shape to an annular shape. The annular inlet portion is designed to have an effective cross sectional area which is smaller than the effective cross-sectional area of the outlet 12 immediately downstream of the impeller 18. The purpose of this differential area will be made apparent in the following description.

It will be noted from FIG. 1 that the wall 13 is joined with the wall 14 by a relatively sharp curve 22, this curve blending smoothly into the inner surface of the wall 14.

The impeller proper is suitably secured to the inner end of the shaft 17, and in the form of the invention illustrated includes a main body 23 of substantially frusto conical form, the outer surface of the body flaring outwardly to give the body a concave conoidal etl'ect, this surface fairing smoothly into the inner surface of the second outlet wall 15. This second wall may be termed a back wall or a wall most remote from the inlet.

The body 23 has a plurality of spirally curved slots 2 formed therein, each of which receives the thickened or base end of a fan blade 25. In this fan a minimum number of blades are provided, four being selected as the optimum number. These fan blades are helically curved and are disposed entirely within the curved or flared portion of the passage connecting the inlet Ill and outlet 12. As a matter of fact, the leading edges of the blades are located substantially in registration with the initial portion of the curve 22 in the outer Wall of the passage, while the trailing edges of the blades extend from a line disposed on the hub approximately one-half of the distance, or 45, around the turn in the passage to a point on the outer wall of the outlet just beyond the end of curve 22. Due to the helical twist of the blades and the chordal length thereof adjacent the hub, the leading and trailing edges of adjacent blades overlap slightly at the hub ends. This arrangement, as previously mentioned, locates the blades entirely within the curved portion of the passage. The outer or peripheral ends of the blades are curved and terminate in closely spaced relation tothe curved surface 22 of the outer wall of the passage. These surfaces serve when the fan impeller is rotating to, in effect, remove any boundary layer air tending to cling to the surface 22. The fan blades are held in the hub by a plurality of bolts 26 which extend axially through the hub and through the thickened base portions of the blades 25. The hub is secured to the shaft by providing the latter with a nut 27 on the threaded outer end. Keys 28 prevent relative rotation between the impeller and the shaft.

It will be noted from FIG. that the stator elements are tilted to impart a preswirl to the air drawn into the passage by the impeller. This tilt or inclination extends in a direction opposite to that of the rotation of the fan. As previously mentioned, the stator elements are adjustable to permit this angle to be varied. However, after adjustment to provide the fan with the greatest efliciency, the stator elements Will be locked in place. The angle opposed to the direction of fan rotation has been selected to cause the air entering the fan and delivered therefrom to ilow substantially radially in all directions from the outlet l2. This direction of flow is in contrast to the flow from the usual or conventional centrifugal fans wherein the air flows Without swirl, or in some cases it is caused to swirl in the same direction as the fan revolves, and such air leaves the fan substantially tangentially. In most conventional centrifugal fans the air is collected, after leaving the rotor, in a scroll, the outlet of which extends tangentially.

One of the features of this invention is to cause the air drawn into the passage to be diffused as it passes from the leading to the trailing edge of the fan blades. This feature is accomplished in part by the change in cross-sectional area of the passage from the inlet to the outlet, the outlet being at least 1.5 times as large as the inlet.

The preswirl at the inlet and substantially no swirl at the exit of the impeller also contribute to the diifusing operation. In order to achieve such a large diffusion without flow separation, the impeller blades cover the major diffusing part along the shroud and hub walls. By reducing the velocity of the air as it passes the rotating blades, stall or separation of the air from the passage walls is prevented.

It will be noted that the fan blades are of considerable transverse length at the hub ends and much smaller length at the peripheral ends. The pitch of these blades also varies from the hub to the peripheral end portions. By providing relatively sharp turns in the passage, and locating the fan blades in the curved portion of the passage, the height of the fan can be kept at a minimum. A reduced diameter is also possible because of no diffuser vanes and no scroll at the exit of the fan. With the fan dimensions at a minimum, the fan is made most suitable for use in ground efl'ect machines.

I claim:

1. A fluid-moving fan, comprising:

(a) housing means forming a passage with a tubular inlet portion and an outlet portion with radially extending first and second walls spaced axially relative to the inlet portion, the wall of the tubular inlet being connected with the first wall of the outlet by a relatively small radius;

(b) an impeller rotor supported in said housing means for rotation about the axis of said inlet, said impeller having a hub which cooperates with said housing means to provide the passage inlet with an annular cross section having an area bearing a predetermined inverse ratio to that of said outlet, the surface of said hub forming a turn in said passage from axial to radial direction and fairing smoothly into the second Wall of the outlet; and

(c) a plurality of blades projecting from said hub, the leading edges of said blades extending across said inlet in a plane substantially at right angles to the axis thereof, the trailing edges of said blades extending from a line on said hub between one-half and three-quarters of the distance around said turn from the inlet to the first wall of the outlet at the downstream end of said small radius, the peripheral edges of said blades being curved and disposed in closely spaced relation to the outer wall of said passage at said small radius, said blades causing fluid to flow of high velocity at the inlet and decreasing velocity as the fluid flows past the fan blades.

2. A fluid-moving fan, comprising:

(a) housing means forming a passage with a tubular inlet portion and a radially directed annular outlet portion with walls spaced axially relative to said inlet portion;

(b) a conoidal insert in said tubular inlet portion to provide the same with an annular cross section having a predetermined area, the walls of said outlet portion being spaced sufficiently to make the effective outlet area at least 1.5 times that of the inlet area;

(c) inlet guide vanes extending radially across said annular inlet portion of said passage, said guide vanes being tilted to impart swirl in a predetermined direction to fluid flowing through said passage;

(d) an impeller rotor supported in said housing means for rotation about the axis of said inlet portion, said impeller having a hub with a surface at the front end aligned with that of said conoidal insert and daring outwardly to smoothly coincide at the back end with the outlet wall most remote from the inlet portion; and

(e) a plurality of blades projecting from said hub, the width of said blades adjacent said hub extending along the flared surface thereof at least the first half of the distance from the beginning of said flared portion to the last-mentioned outlet wall, the outer ends of said blades terminating in closely spaced relation to the outer wall of the passage, said rotor blades being twisted and rotating with said hub in a direction opposed to the direction of swirl imparted to the fluid by said guide vanes.

3. A fluid-moving fan, comprising:

(a) housing means having a tubular portion forming an inlet, said tubular portion terminating in a first wall extending substantially radially from said tubular portion, said housing means having a second Wall spaced from said first wall axially relative to said inlet to provide an outlet extending completely around said housing;

(b) a rotor hub supported in said housing for rotation about the axis of said inlet, said rotor hub co- 5 6 operating with the tubular portion of said housing (e) a conoidal spinner element supported by the ind id d ll t o id an annular passage ner ends of said inlet vanes in said inlet, said spinner leading from said inlet to said outlet, the effective e1ement 1f3gi$terif1g f l y With sfiid rotor hub cross-sectional area of said outlet being substantially and gllldlllg flllld 111 831d Inlet Sald vanes and 1.5 times that of said inlet; 5 blades- (e) blade elements projecting from said rotor hub, References Cited by the Examiner blade elements ha ving leading edges disposfid 1n the portion of said inlet having the smallest effective cross-sectional area and trailing edges at 3 3 1 least 45 around the turn in said passage from the 10 1785460 12/30 S a? g T 2 axial to the radial direction, said blade elements be- 0 er 1,954,194 4/34 Briggs 2s3 117 mg twisted to cause flllld flow from the inlet toward 2,848,190 8/58 Barr 230--134.45 the outlet upon rotation of said hub and blades;

(d) a plurality of inlet vanes extending radially in- 15 FOREIGN PATENTS wardly from the tubular portion of said housing into 103,027 2/38 Australia. said inlet upstream of said rotor hub, said vanes 1,003,749 11/51 France. being tilted to cause fluid passing through said inlet 170,885 3/ 60 SWEdeIl.

to flow toward the approaching leading edges of said JOSEPH BRANSON primary Examiner blade elements; and 

1. A FLUID-MOVING FAN, COMPRISING: (A) HOUSING MEANS FORMING A PASSAGE WITH A TUBLUAR INLET PORTION AND AN OUTLET PORTION WITH RADIALLY EXTENDING FIRST AND SECOND WALLS SPACED AXIALLY RELATIVE TO THE INLET PORTION, THE WALL OF THE TUBULAR INLET BEING CONNECTED WITH THE FIRST WALL OF THE OUTLET BY A RELATIVELY SMALL RADIUS; (B) AN IMPELLER ROTOR SUPPORTED IN SAID HOUSING MEANS FOR ROTATION ABOUT THE AXIS OF SAID INLET, SAID IMPELLER MEANS TO PROVIDE THE PASSAGE INLET WITH AN ANNUING MEANS TO PROVIDE THE PASSAGE INLET WITH AN ANNULAR CROSS SECTION HAVING AN AREA BEARING A PREDETERMINED INVERSE RATIO TO THAT OF SAID INLET; AND SURFACE OF SAID HUB FORMING A TURN IN SAID PASSAGE FROM AXIAL TO RADIAL DIRECTION AND FAIRING SMOOTHLY INTO THE SECOND WALL OF THE OUTLET; AND (C) A PLURALITY OF BLADES PROJECTING FROM SAID HUB, THE LEADING EDGES OF SAID BLADES EXTENDING ACROSS SAID INLET IN A PLANE SUBSTANTIALLY AT RIGHT ANGLES TO THE AXIS THEREOF, THE TRAILING EDGES OF SAID BLACES EXTENDING FROM A LINE ON SAID HUB BETWEEN ONE-HALF AND THREE-QUARTERS OF THE DISTANCE AROUND SAID TURN FROM THE INLET OF THE FIRST WALL OF THE OUTLET AT THE DOWNSTREAM END OF SAID SMALL RADIUS, THE PERIPHERAL EDGES OF SAID BLADES BEING CURVED AND DISPOSED IN CLOSELY SPACED RELATION TO THE OUTER WALL OF SAID PASSAGE AT SAID SMALL RADIUS, SAID BLADES CAUSING FLUID TO FLOW OF HIGH VELOCITY AT THE INLET AND DECREASING VELOCITY AS THE FLUID FLOWS PAST THE FAN BLADES. 